PSYC 351: Chapter 4 - Pavlovian Conditioning: Basic Concepts
PSYC 351: Fundamentals of Learning - Chapter 4: Pavlovian Conditioning: Basic Concepts
Questions to Ponder
Do certain songs evoke special meaning (e.g., nostalgia, sadness)?
Do some perfume smells trigger an unpleasant reaction?
Do you have a phobia (e.g., fear of dogs)?
Is there a specific food or drink you cannot consume due to a past experience (e.g., taste aversion)?
Outline
Pavlovian Conditioning Background
Pavlovian Conditioning Paradigms
Aversive Conditioning
Going away from something we dislike
Appetitive Conditioning
Going towards something we like
Influencing Factors of Pavlovian Conditioning
What Makes An Effective Conditioned Stimulus (CS) & Unconditioned Stimulus (US)?
The Man Who Started It All: Ivan Petrovich Pavlov
1904 Nobel Prize: Awarded for his work on the role of insulin in digestion.
Shift in Research Focus: Initially focused on hormones in digestion, moving away from the nervous system's role.
New Perspective: Pavlov took a novel approach, concentrating on associative learning.
Proposed that new reflexes to stimuli could be acquired through learning.
This involved the formation of associations between stimuli.
He sold dog saliva/bile to fund his research (gross)
Modifying Reflexes Through Learning
The purpose of classical conditioning is to make predictions about our environment (successful = higher survival chance)
If you can predict when food will come, and make saliva response in anticipation of food, your eating and digestion will go better, and therefore you will have better chances of survival
Salivary Reflex: A crucial reflex in digestion, it involves the salivary response to food.
Fistula: Pavlov used a surgical procedure to create a fistula, allowing for accurate measurement of salivary output.
Initial Observation: Dogs naturally salivated upon receiving food.
Accidental Discovery: Over time, dogs began salivating to previously neutral stimuli associated with food, such as the sight of food, the lab technician, or even the sound of their footsteps.
Intentional Experimentation: Pavlov then intentionally used a completely unrelated stimulus, like a bell, to study this phenomenon.
It’s All About Reflexes
Definition of Reflexes: Involuntary responses to a stimulus.
End Result of Pavlovian Conditioning (PC): The formation of a conditioned 'reflex' to a once neutral stimulus.
Types of Reflexes:
Unlearned (Unconditioned): Innate, natural responses (e.g., salivation to food).
Learned (Conditioned): Acquired responses through associative learning (e.g., salivation to a bell).
Pavlov's Setup and Findings
Setup: Dogs were placed in an observation screen, with a device to collect and count drops of saliva. Meat powder was presented, and a revolving drum recorded responses.
Before Conditioning Trials:
Food \rightarrow Salivation
Unconditional Stimulus (US): Food (automatically produces a response without prior learning).
Unconditional Response (UR): Salivation (the automatic, unlearned reflex to the US).
Neutral Stimulus (NS): Bell (a stimulus to which the organism does not initially respond).
After Conditioning Trials:
Bell \rightarrow Salivation
Conditional Stimulus (CS): Bell (the neutral stimulus that, after repeated pairings with a US, produces a response).
Conditional Response (CR): Salivation (the learned response made to the CS).
Criticality: Object learning is fundamental for Pavlovian conditioning.
Definition of Pavlovian Conditioning
A form of learning where an association is formed between one stimulus and another.
Stimulus: Any event or object in the environment.
Transformation: In PC, a 'neutral' stimulus becomes an 'important' stimulus through this learning process.
Key Terms Defined
NS (Neutral Stimulus): A stimulus that does not initially evoke a specific response from the organism.
NS becomes CS with learning
US (Unconditioned Stimulus): Any stimulus that unconditionally (automatically) produces an unlearned response without any prior training.
UR (Unconditioned Response): The automatic, unlearned, reflexive response made naturally to the unconditioned stimulus.
CS (Conditioned Stimulus): The formerly neutral stimulus that, after consistent pairings with an unconditioned stimulus, comes to elicit a conditioned response.
CR (Conditioned Response): The learned response made to the conditioned stimulus, which is often similar to, but not always identical to, the UR.
Pavlov's Dogs Example:
Reflexive line: US (Meat) \rightarrow UR (Salivation)
Pairing line: NS (Bell) \rightarrow US (Meat)
Result: CS (Bell) \rightarrow CR (Salivation)
Important note: the dogs don’t learn to droll cause of the bell — that is the manifestation/result of the learning. The learning is that the bell predicts the food (so the dog might as well salivate)
The learning: the CS comes to predict the US (bell predicts the food)
Because you’ve learned that, you make an anticipatory reflex ahead of time (CS is outward display of learning, not learning itself)
Characteristics of Pavlovian Conditioning
Speed: Can occur quickly, sometimes in as few as 5 or 6 pairings, and even in just 1 pairing for certain types of conditioning (e.g., taste aversion).
Timing (Temporal Relationship): Most likely to occur if the CS is presented before the US.
Less likely if the CS and US are presented simultaneously.
Almost never occurs if the CS is presented after the US.
Nature of Response: Involves involuntary responses such as salivation, fear, happiness, surprise, etc.
Prevalence: Widespread throughout the animal kingdom, but not as ubiquitous as habituation (e.g., protozoans generally do not exhibit PC).
Human Learning Examples
Taste Aversions:
Avoiding a specific alcoholic drink after a heavy night of drinking where sickness occurred.
Developing an aversion to sushi after experiencing nausea on a roller coaster.
Phobias:
Fear of bees, dogs, spiders, etc.
Little Albert: A famous experiment where a 9-month-old baby was conditioned to fear a white rat.
Test Anxiety: Developing anxiety symptoms in response to test-related stimuli due to past negative experiences.
Fear of Failure: When failure becomes associated with an unpleasant experience (e.g., punishment), leading a person to avoid taking risks.
Role in Medicine
Chemotherapy-Induced Aversions: Cancer patients undergoing chemotherapy often experience intense nausea, leading to the development of aversions to many foods due to their association with the treatment.
Human Example: Altoids and Noise (The Office - Jim & Dwight)
Reflexive line: US (Altoids) \rightarrow UR (Acceptance/Reaching for Altoid/Salivation)
Pairing line: NS (Noise - a specific computer sound) \rightarrow US (Altoids)
Result (After Conditioning): CS (Noise) \rightarrow CR (Salivation/Wanting Altoid/Reaching for Altoid)
Related Phenomena
Generalization: Occurs when a stimulus that is similar to the CS elicits the CR.
Example: If bitten by one dog, a person might develop a fear not just of that specific dog, but of all dogs.
Adaptiveness: Often adaptive, as it allows organisms to respond to novel, but similar, threats or opportunities.
Discrimination: Occurs when the CR is made only to the specific CS and not to any other similar stimuli.
Example: After a negative experience with one type of alcohol (e.g., tequila), a taste aversion may develop exclusively to tequila and not generalize to other types (e.g., whiskey, rum, vodka).
Pavlov’s Dogs & Tones
If dogs are conditioned to salivate only to a specific tone (e.g., middle c note piano)
most prmoninent or salient aspect of stimulus is used for prediction
Conditioning and Emotions
Watson & Rayner (1920) - Little Albert
Conditioned child to become fearful of white fluffy rat
CS (or NS) whtie fluffy rat paired with loud bang produced conditioned response of crying/fear
white fluffiness charactewristic was learned about it, so kid generalized to all white fluffiness — santa hat and rabbit produced fear response
Meaninguflness, intensity, age —- factors that can help us predict if something will become generalized or not
Appetitive Conditioning
Pavlovian Conditioned Approach
Daily 60-min sessions
CS: 15 sec white noise
US: 0,3mll of 10% sucrose
Paired rats
CS - US, 10 pairings per sessions
Unpaired rats
10 CS and 10 US, independently
Control by examining total port entries
No differences in motor abilities, motivation, etc…
Quail Sex Conditioning
Exposure to a female (US) innately produces arousal (UR)
CS is a tone or light
After pairing the CS with the US, the CS comes to produce approach (CR)
Sign Tracking (Autoshaping)
Tendency to approach appetitive stimuli (e.g., stimulus that signals food)
They had a little light that was predictive of US
some pigeons, when light came to predict US, they wouldn’t go to food port where the food was given, they would approach and interact with the light as if the light was food.
Light: food (arrow) pecking
Light: pecking, directed at light
Rat fucking the pilon example
Individual differences challenge the notion that US-CS pairings result in predictable CRs
Perhaps the nature of the CR depends on the salience of the mental representations of the CS and US
Greater salience of the CS = sign tracking
Greater salience of the US = goal tracking
Sign Tracking (ST) behaviours have been related to drug addiction
Sign tracking rats display exaggerated sensitization to cocaine and are more sensitive to cues that signal cocaine compared to goal tracking rats
Sign tracking is also related to attentional deficits, risk-taking, and impulsivity
Aversive Conditioning Paradigms
Odour Conditioning
Exposure to shock (US) innately produces escape/avoidance behaviour (UR)
CS is an odour
After CS is paired with US, CS comes to produce avoidance (CR)
Can work with only one trial
Aversive conditioning:
New CS → CR reflex helps avoid noxious US
Fear Conditioning in Animals
Conditioned emotional response procedure
Conditioning Taste Aversion
2 groups (Smith & Roll, 1967)
Control group is line at top
Gave rats one trial to get exposure to a brand new taste (juice, fake sugar)
Experimental group
Gave rats one trial to get exposure to a brand new taste (juice, fake sugar) that was x-rayed (inducing sickness)
Flavour (CS) becomes predictive of sickness that followed, they choose to avoid juice forever
one-trial learning!
Long-delay learning
Strong aversion
Conditionied taste aversion is easy to learn because it is essential for survival (eat the wrong thing and die)
Eye Blink Conditioning
In human and nonhuman animals
CS = Light, tone, or mild vibration to stomach
Conditioning takes hundreds of trials
Puff of aire to eye (US) innately produces eyeblink (UR)
CS is a tone or light, comes to produce gradual eye closure (CR)
A form of aversive conditioning: CS → CR prepares to avoid US
Their way of avoiding the puff of air (preventative)… reactionary blink becomes preventative blink!
ha different characeristics than reflex… speed, force, and duration are different
Works on rabbits and humans, but takes many trials
Conditioned Compensatory Response
A CR that is the opposite of the UR, helping to balance/correct for the US-UR reflex
Inject adrenaline (US) → heart rate increase (UR)
Repeat the procedure in the same testing chamber (CS)
Eventually, CS comes to produce a decrease in heart rate (CR) that helps maintain homeostasis (balance) against expected adrenaline injection
We observe this as a tolerance, as the testing chamber evokes a CR that weakens the overall effects of the drug
Note the importance of the drug CONTEXT (e.g., testing chamber) in enabling tolerance
Influencing Factors for PC
Four factors influence strength and time required for Pavlovian conditioning:
The number of pairings of the CS (e.g., bell) and the US (e.g., meat)
The more pairings, the stronger the CR
The intensity of the US
e.g., a squeak versus a roar
The more intense the US the faster conditioning occurs
How reliably the CS (e.g., bell) predicts the US (e.g., meat)
The more reliable the better
Rat example:
G1: Tone + shock paired 20 times
G2: same as G1 but also given 20 unpaired shocks
It is all about being able to predict (that’s the utility of Classical Conditioning)
The temporal relationship between the CS (e.g., bell) and the US (e.g., meat)
The less the elapsed time the better (half a second)
Taste aversions can be exceptions to this rule
The nS should be presented BEFORE the unconditioined stimulus (tone before meat)
Not at same time or after)
What Makes an Effective CS & US?
Initial response to the stimuli (Pavlov)
CS does not initially elicit the conditioned response
Generally speaking, the CS should have no meaning
US elicits target response without prior training
Generally speaking, the US should have meaning
What matters is the relative identification, depending on the pairing order
Significance and discriminability
i. intensity/salience (a snickers bar vs. a whole bag of them)
Give MORE:
Make the US more relevant to the biological needs of the organism
Larger quantity
Something needed by organism
Make it NATURALISTIC:
Makes the CS more similar to the kinds of stimuli than an animal will encounter in its natural environment
ii. Novelty of the stimuli
CS-preexposure effect (latent inhibition)
Previous exposure without meaning produced learning, probably habituation (lets ignore that idiot and his bell), so then learning that this same thing has now gained a new meaning will take it longer for learning
CS-US relevance/belongingness
“Belongingness” or “associative bias”
Experiment:
Water deprived rats
Put them in cage with water spouts
When they drank water, they drink new flavour and are exposed to lights and sound
Then split rats into two groups:
Half made sick through injections of lithium fluoride
Other half given a shock
Then half of each group put back into separate test chamber again, with either new taste or audiovisual components
Drinking was decreased with new flavour, but not with audiovisual cue with sickness rats (new taste goes better with sickness than audiovisual components)
Drinking was normal with new flavour, decreased with audiovisual cue with shock rats (audiovisual components go better with shock than taste)
Let’s Design a Pavlovian Experiment
Research Question:
Does chemotherapy cause conditioned taste aversion in young children?
Procedure:
Identify patients who are undergoing chemotherapy
Divide them into three groups
Matched for age, sex, intensity of chemotherapy, etc.
Experimental Design:
Conditioning Phase
G1 - Novel ice-cream flavour, then get chemotherapy
G2 - Play with toy, then get chemotherapy
G3 - Novel ice-cream flavour, no chemotherapy
Test Phase
Give all patients a choice
Eat the novel ice-cream flavour again or play a game
Calculate preference for eating ice cream
(# patients chose ice-cream/total # patients)
Why are Control Procedures Needed?
Pseudoconditioning:
Sensitization:
Random control procedure:
Present the US periodically during both the CS and the ITI
Explicitly unpaired control:
• – Identify patients who are undergoing chemotherapy
– • Matched for age, sex, intensity of chemotherapy, etc.
Divide them into 3 groups
Procedure:
• – • Group 1: Novel ice-cream flavour, then get chemotherapy
• Group 2: Play with toy, then get chemotherapy
• Group 3: Novel ice-cream flavour, no chemotherapy
Conditioning phase
– • – Eat the novel ice-cream flavour again or play a game
Give all patients a choice
• – (# patients chose ice-cream/total # patients